Fully Inkjet‐Printed Transparent Oxide Thin Film Transistors Using a Fugitive Wettability Switch

Jang, Jaewon; Kang, Hongki; Chakravarthula, Himamshu C. Nallan; Subramanian, Vivek

doi:10.1002/aelm.201500086

Cited by 108 publications

(97 citation statements)

References 41 publications

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“…Moreover, fully printed TFTs show degraded performance due to the poorer quality of printed semiconductors and dielectrics compared to their conventional counterparts. [12][13][14] An alternative approach of microelectromechanical (MEM) relays with movable cantilevers operated by electrostatic wileyonlinelibrary.com state. We also develop an analytical model to calculate the turnoff voltage ( V TOF ) using differential beam bending theory with superposition of movable reed defl ection by the gate actuation force and the residual beam bending moment.…”

Section: Introductionmentioning

confidence: 99%

Fully Inkjet‐Printed Stress‐Tolerant Microelectromechanical Reed Relays for Large‐Area Electronics

Karim

Chung

Alon

et al. 2016

Adv Elect Materials

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actuation can provide a solution for ultralow leakage devices with hyper-abrupt switching. [ 15 ] These deliver low leakage, excellent subthreshold swing, and very low on-resistance. Considering all the benefi ts of MEM relays over printed TFTs, printed MEM relays have been proposed as a new switching devices for low-power and large-area electronics. [ 16,17 ] Inkjet-printing is attractive for the fabrication of MEM relays due to its mask-free, vacuum-independent, low-temperature, and environment-friendly processability. [ 16 ] Although the previously reported printed MEM relays showed superior performance in terms of very low on state resistance ( R ON ) and minimal off current ( I OFF ), unfortunately, these structures are vulnerable to stress variations in the printed cantilevers that can cause the suspended beam to curl up. This happens due to the stress gradient built up across the thickness of the fi lm. [ 18 ] An in-plane tensile stress develops in the fi lm formed from the nanoparticle-based ink during the constrained sintering process. [ 19 ] However, a positive gradient of the tensile stress is also built up across the thickness of the fi lm as a result of the fi lm morphology variation caused by the differential sintering rate in the nanoparticulate cantilever layer. The scanning electron microscope (SEM) images presented in Figure S1 (Supporting Information) show different morphology at the top and the bottom of the fi lm formed from sintered silver nanoparticles. In addition to causing increased device-to-device variation, this phenomenon can increase the electrostatic actuation gap, making the MEM relays inoperable in reasonable actuation voltage ranges. Additionally, in the previously reported printed MEM relays, only the cantilever and post structure was inkjetprinted while the sacrifi cial layer was deposited using spincoating, [ 16,17 ] which leads to a poor area scalability. Therefore, a new approach in MEM relay structural design and sacrifi cial layer processing is necessary to make it viable for realistic largearea electronics realization.In this paper, we demonstrate the fi rst MEM relay with a printed sacrifi cial layer, which makes it realizable for large-area systems; the relay implements a novel reed-relay structure that provides immunity to the stress variations in the printed cantilevers. We introduced a second cantilever with higher stiffness over the switching cantilever to block the upward curling of the movable cantilever. The proposed MEM relay resembles a reed switch structure with the two reeds in a normally closed

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Section: Introductionmentioning

confidence: 99%

Fully Inkjet‐Printed Stress‐Tolerant Microelectromechanical Reed Relays for Large‐Area Electronics

Karim

Chung

Alon

et al. 2016

Adv Elect Materials

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“…(3 of 6) 1500326 wileyonlinelibrary.com as 12 µm, having resistivity of 0.01-0.02 Ω cm, comparable to that obtained using direct inkjet and gravure printing with similar precursors. [ 18,19 ] In general, we fi nd that metal-acetate precursors such as zinc acetate deposit with a small gap (2 ± 0.5 µm) between the polymer template and the patterned feature. In contrast, the selectivity of a representative metalchloride precursor-based spray solution (tin-chloride) is illustrated in Figure 1 , showing that a larger gap of 25 µm ± 3.0 µm is formed between the hydrophobic template and the patterned features.…”

Section: Wileyonlinelibrarycommentioning

confidence: 99%

“…Although shadow-mask-based patterning has been demonstrated for spray-deposited metal oxide transistors, [ 17 ] the resolution (≈500 µm) and performance ( µ max ≈ 0.18 cm 2 V −1 s −1 ) were limited compared to reports of inkjet printed thin fi lm transistors (TFTs) fabricated at similar temperatures. [ 18 ] To fully realize the benefi ts of spray pyrolysis in thin fi lm oxide transistors, a new low cost patterning approach is required.Here, we leverage the high performance of TCO fi lms deposited via spray pyrolysis along with the fl exibility of drop-ondemand inkjet printing to demonstrate the selective deposition of scalable, high-performance metal oxide thin-fi lm transistors, addressing a technological need for high-throughput patterning of these materials, and providing a unique advantage over sputtering. Here, we show that the characteristic sensitivity of spray deposition to substrate surface energy offers the key to facilitating patterned fi lm growth in situ, using a hydrophobic polymer template obtained by low-cost, scalable printing techniques.…”

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confidence: 99%

Patterning of Solution‐Processed, Indium‐Free Oxide TFTs by Selective Spray Pyrolysis

Zeumault

Scheideler

Grau

et al. 2015

Adv Elect Materials

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by X-ray refl ectivity has shown that spray-pyrolysis fi lms of materials such as indium-gallium-zinc oxide have signifi cantly lower porosity than spin-coated fi lms of a comparable thickness, [ 12 ] ultimately leading to improved mobility and bias-stress stability.Although spray pyrolysis offers the potential to deposit highquality TCOs at a low cost over large areas, it remains a blanket deposition technique that requires more expensive patterning techniques such as photolithography and etching for fabricating multilayer patterned structures such as thin-fi lm transistors. [ 13 ] These additional patterning steps limit throughput and contribute additional process complexity and cost. [14][15][16] Thus, lacking integration with highly scalable patterning methods, spray pyrolysis may have limited practical applications in large-area-electronics as it remains, in some sense, a cheaper substitute for sputtering with the fl exibility of solutionprocessing. Although shadow-mask-based patterning has been demonstrated for spray-deposited metal oxide transistors, [ 17 ] the resolution (≈500 µm) and performance ( µ max ≈ 0.18 cm 2 V −1 s −1 ) were limited compared to reports of inkjet printed thin fi lm transistors (TFTs) fabricated at similar temperatures. [ 18 ] To fully realize the benefi ts of spray pyrolysis in thin fi lm oxide transistors, a new low cost patterning approach is required.Here, we leverage the high performance of TCO fi lms deposited via spray pyrolysis along with the fl exibility of drop-ondemand inkjet printing to demonstrate the selective deposition of scalable, high-performance metal oxide thin-fi lm transistors, addressing a technological need for high-throughput patterning of these materials, and providing a unique advantage over sputtering. Here, we show that the characteristic sensitivity of spray deposition to substrate surface energy offers the key to facilitating patterned fi lm growth in situ, using a hydrophobic polymer template obtained by low-cost, scalable printing techniques. By this versatile method, we fabricate high-performance oxide TFTs (mobility ≈ 30 cm 2 V −1 s −1 , subthreshold swing ≈ 400 mV dec −1 ) in which the semiconductor, gate dielectric and source-drain layers are all deposited using solution-processing techniques at a maximum processing temperature of 350 °C. In addition, we exploit the characteristic surface selectivity of the spray-pyrolysis deposition to fabricate conductive SnO 2 :Sb (antimony-doped tin oxide (ATO)) lines as narrow as 12 µm having a conductivity of 65 S cm −1 , which would otherwise be diffi cult to achieve by direct printing. To our knowledge, this is a fi rst demonstration of selectively deposited spray pyrolysis fi lms and a fi rst report of the integration of spray pyrolysis with printing for high-throughput patterning of metal oxide TFTs.Figure 1 a shows the process fl ow used in this work for patterning metal oxide TFTs by selective spray pyrolysis.

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“…This serves to facilitate formation of small, welldefined printed patterns, and is burned off during the subsequent annealing. The overall process flow used to fabricate inkjet printed oxide TFTs is shown below [7]. All layers are based on sol-gel transparent precursors, including antimony doped tin oxide conductors, tin oxide semiconductor, and zirconia dielectric.…”

Section: Printed Organic Thin Film Transistorsmentioning

confidence: 99%

71-2:Invited Paper: Printed Transistors and MEMS for Large-Area Electronics

Subramanian

Chung

Grau

et al. 2016

SID Symposium Digest of Technical Papers

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Printing is a promising process technology for realization of lowcost, large area, and flexible electronic systems. To realize printed electronics, it is necessary to develop technologies for fabrication of printed devices such as transistors, etc., including development of the requisite printable materials, the underlying printing process technologies, and the integration strategies for fabrication of printed devices. This paper reviews our development of a wide range of printed switching devices, including printed organic transistors, printed inorganic transistors based on transparent oxides, and printed microelectromechanical switches.

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Fully Inkjet‐Printed Transparent Oxide Thin Film Transistors Using a Fugitive Wettability Switch

Cited by 108 publications

References 41 publications

Fully Inkjet‐Printed Stress‐Tolerant Microelectromechanical Reed Relays for Large‐Area Electronics

Fully Inkjet‐Printed Stress‐Tolerant Microelectromechanical Reed Relays for Large‐Area Electronics

Patterning of Solution‐Processed, Indium‐Free Oxide TFTs by Selective Spray Pyrolysis

71-2:Invited Paper: Printed Transistors and MEMS for Large-Area Electronics

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